Deaminering

Deaminering, or deamination, is the removal of an amino group (-NH2) from an organic molecule. In biochemistry it is a central step in the catabolism of amino acids and in nucleotide metabolism. The removed nitrogen is typically released as ammonium (NH4+) and must be disposed of, most often through the urea cycle in animals.

There are several forms of deamination. Oxidative deamination is catalyzed by enzymes such as glutamate dehydrogenase and converts an amino group to ammonia while yielding a corresponding α-keto acid (for example glutamate to α-ketoglutarate). Hydrolytic deamination uses water to remove the amino group, as seen in certain amino acid deaminases. Deamination is distinct from transamination, in which an amino group is transferred from one molecule to another rather than released as ammonia.

In mammals, deamination occurs mainly in the liver and, to a lesser extent, in the kidneys. The resulting α-keto acids can enter the citric acid cycle for energy production, or serve as substrates for gluconeogenesis or other biosynthetic pathways. The liver also detoxifies ammonia by converting it to urea via the urea cycle.

In nucleic acid metabolism, specific deaminases remove amino groups from nucleotides, for example cytosine deaminase converting cytosine to uracil and adenosine deaminase converting adenosine to inosine. These reactions have implications for DNA/RNA editing and immune defense in some organisms.

Deamination is distinct from deamidation, which involves removal of an amide group from amide-bearing biomolecules and often affects protein structure rather than nitrogen disposal.